Pharmacology · Class
Anticoagulant reversal agents !
Antidotes that switch off an anticoagulant when there is serious bleeding or urgent surgery. Each one fits a specific drug.
Updated 2026-11-01
What they are
Medicines that undo the effect of an anticoagulant: vitamin K and prothrombin complex concentrate for vitamin K antagonists, protamine for heparin, idarucizumab for dabigatran and andexanet alfa for the factor Xa inhibitors.
Mechanism of action
They work in three ways. Some bind the anticoagulant and take it out of action: protamine (a strongly basic protein) neutralises acidic heparin, idarucizumab is an antibody fragment that holds dabigatran, and andexanet alfa is a decoy factor Xa that captures apixaban or rivaroxaban. Vitamin K lets the liver make working clotting factors again, which takes hours. Prothrombin complex concentrate replaces the missing factors directly and acts within minutes.
Target: The anticoagulant itself, or the clotting factors it lowers
Drugs in this class
- Phytomenadione (vitamin K1)Vitamin K1 as a medicine. It lets the liver make working clotting factors again: it reverses warfarin and prevents…Vitamin K-dependent gamma-glutamyl carboxylase (GGCX), which uses vitamin K as its cofactor
- Protamine sulfateA strongly basic fish protein that binds heparin and cancels its effect within minutes. It can cause severe drops in…Heparin (binds the drug itself)
- IdarucizumabA humanised antibody fragment that grabs dabigatran and quickly switches off its effect, for urgent surgery or…Dabigatran (binds the drug itself)
- Andexanet alfaAn inactive decoy copy of factor Xa that soaks up apixaban or rivaroxaban, used when they cause life-threatening…Factor Xa inhibitors (apixaban, rivaroxaban), which it captures
Others in the class
- prothrombin complex concentrate
- fresh frozen plasma
Test yourself
Think of the answer, then tap the question to see it.
Which antidote matches each anticoagulant: heparin, warfarin, dabigatran, apixaban?
Heparin: protamine. Warfarin: vitamin K, plus prothrombin complex concentrate for serious bleeding. Dabigatran: idarucizumab. Apixaban: andexanet alfa.
Why is vitamin K alone too slow for life-threatening bleeding on warfarin?
The liver needs hours to make new working factors after vitamin K is given; prothrombin complex concentrate supplies the factors at once.
Why does protamine have no effect on apixaban?
Protamine works by binding the negatively charged heparin chains; apixaban is a small molecule that binds factor Xa directly, so there is nothing for protamine to neutralise.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - PROTAMINE SULFATE injection, solution (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - PHYTONADIONE injection, emulsion (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - APIXABAN tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.